This the rooftop area of the Mass Fusion Building. This is your landing zone via vertibird during the BoS quest, Spoils of War and the relay point of The Institute quest Mass Fusion. The elevator requires an ID card.Search the desk on the upper floor to find the Mass Fusion Executive Lab Password and Mass Fusion Executive ID. Access the lab nearby and use the terminal. Read the first intra-mail entry to learn the location of the agitator. You can also find the Oslow's Office Recording holotape in the same room. Now go to the elevator down, swipe the ID card and ride it down to the building interior.